A 44-year-old man, a known alcoholic and heavy smoker, was hospitalized with high fever and respiratory failure which a few hours later required intubation and artificial ventilation, although the chest x-ray had been unremarkable. Later serial chest x-ray films showed intrapulmonary infiltrations, while Legionella Bozemanii was demonstrated by direct immunofluorescence. Cranial computed tomography was unremarkable, despite the onset of tetraparesis and a severe midbrain syndrome. Cerebrospinal fluid contained merely mild lymphocytic pleocytosis. However, magnetic resonance imaging revealed symmetrical demyelinization foci in the brainstem as a sign of encephalitis. The neurological deficits regressed almost completely after several weeks of antibiotic treatment and rehabilitation measures over several months.